<h2>题目编号 : 96</h2>
<div style="color:#666;font-size:80%;">27 May 2005</div><br />
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<p>Su Doku (Japanese meaning <i>number place</i>) is the name given to a popular puzzle concept. Its origin is unclear, but credit must be attributed to Leonhard Euler who invented a similar, and much more difficult, puzzle idea called Latin Squares. The objective of Su Doku puzzles, however, is to replace the blanks (or zeros) in a 9 by 9 grid in such that each row, column, and 3 by 3 box contains each of the digits 1 to 9. Below is an example of a typical starting puzzle grid and its solution grid.</p>
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<td style='font-family:courier new;font-size:14pt;'>0 0 3<br />9 0 0<br />0 0 1</td>
<td style='font-family:courier new;font-size:14pt;'>0 2 0<br />3 0 5<br />8 0 6</td>
<td style='font-family:courier new;font-size:14pt;'>6 0 0<br />0 0 1<br />4 0 0</td>
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<td style='font-family:courier new;font-size:14pt;'>0 0 8<br />7 0 0<br />0 0 6</td>
<td style='font-family:courier new;font-size:14pt;'>1 0 2<br />0 0 0<br />7 0 8</td>
<td style='font-family:courier new;font-size:14pt;'>9 0 0<br />0 0 8<br />2 0 0</td>
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<td style='font-family:courier new;font-size:14pt;'>0 0 2<br />8 0 0<br />0 0 5</td>
<td style='font-family:courier new;font-size:14pt;'>6 0 9<br />2 0 3<br />0 1 0</td>
<td style='font-family:courier new;font-size:14pt;'>5 0 0<br />0 0 9<br />3 0 0</td>
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<td style='font-family:courier new;font-size:14pt;'>4 8 3<br />9 6 7<br />2 5 1</td>
<td style='font-family:courier new;font-size:14pt;'>9 2 1<br />3 4 5<br />8 7 6</td>
<td style='font-family:courier new;font-size:14pt;'>6 5 7<br />8 2 1<br />4 9 3</td>
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<td style='font-family:courier new;font-size:14pt;'>5 4 8<br />7 2 9<br />1 3 6</td>
<td style='font-family:courier new;font-size:14pt;'>1 3 2<br />5 6 4<br />7 9 8</td>
<td style='font-family:courier new;font-size:14pt;'>9 7 6<br />1 3 8<br />2 4 5</td>
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<td style='font-family:courier new;font-size:14pt;'>3 7 2<br />8 1 4<br />6 9 5</td>
<td style='font-family:courier new;font-size:14pt;'>6 8 9<br />2 5 3<br />4 1 7</td>
<td style='font-family:courier new;font-size:14pt;'>5 1 4<br />7 6 9<br />3 8 2</td>
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<p>A well constructed Su Doku puzzle has a unique solution and can be solved by logic, although it may be necessary to employ &quot;guess and test&quot; methods in order to eliminate options (there is much contested opinion over this). The complexity of the search determines the difficulty of the puzzle; the example above is considered <i>easy</i> because it can be solved by straight forward direct deduction.</p>
<p>The 6K text file, <a href='project/sudoku.txt'>sudoku.txt</a> (right click and 'Save Link/Target As...'), contains fifty different Su Doku puzzles ranging in difficulty, but all with unique solutions (the first puzzle in the file is the example above).</p>
<p>By solving all fifty puzzles find the sum of the 3-digit numbers found in the top left corner of each solution grid; for example, 483 is the 3-digit number found in the top left corner of the solution grid above.</p>
<!--<p class='info'>Note: If you're convinced that &quot;guess and test&quot; methods need not be employed please tell how you would solve #6 and #46. (c;</p>-->

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